groundfish noun 1verb 1forms 3 noun1 •Any of many fish that swim near the seafloor: a demersal fish.Boats catching groundfish — fish near the ocean bottom including cod, haddock and halibut — catch thousands of pounds of fish at a time. — 2007 verb1 •To fish for groundfish.Earl, who has lobstered, scalloped, groundfished and run tugs most of his life, is half joking. — 2004 formsgroundfished · groundfishing · groundfishes